The invention relates to an infinitely variable traction roller transmission in which power is transmitted through traction rollers pivotally supported between toric input and output discs.
In such transmissions, the traction rollers are mounted on support structures which, when pivoted, cause engagement of the traction rollers with the toric discs in circles of varying diameters depending on the desired transmnission ratio. The pivotal traction roller support structures are so supported that they can be moved axially for initiating a change in the transmission ratio. For example, two traction rollers may be supported opposite one another by flexible tension sheets as shown in U.S. Pat. No. 4,086,820 which issued May 2, 1978 to Charles E. Kraus.
In U.S. Pat. No. 4,858,484 by Charles E. Kraus in which two traction rollers are arranged between, and in engagement with, opposite toric traction discs for the transmission of motion therebetween, each traction roller is supported by a pivotal support trunnion which has support rollers disposed at opposite ends thereof and supported on partial circular tracks disposed on the housing's inner surface for direct trunnion support. The traction rollers are supported on the pivot trunnions by force transmitting means which, for inexpensive transmissions, include slacks of Belleville springs. The housing tracks may have a center of curvature which is slightly off-set with regard to the pivot axis of the trunnions in order to provide greater compression of the Belleville spring, that is, greater disc engagement forces in one pivotal end position of the pivot trunnions than in their opposite pivotal end positions.
The arrangement according to applicant's application Ser. No. 07/259,043 utilizes a single support roller for each trunnion which is received in a partial circular track section mounted in the housing for forcing the trunnion and the associated traction roller into firm engagement with the toric discs for permitting transmission of motion therebetween. An axially projecting control end of each trunnion is supported so as to be slightly movable in a plane normal to the axis of the toric discs, the control ends of the trunnions having means associated therewith for tilting the trunnions in unison in said plane for the initiation of a transmission ratio change.
In each case the traction roller support trunnions must operate in unison, that is, they must be at the same transmission ratio pivotal position in order to avoid slip. To insure operation of the trunnions in unison the arrangement according to U.S. Pat. No. 4,830,578 utilizes cables extending around pulley structures on the trunnions. However, such cables have experienced breakage as a result of jerky motions of the trunnions.
It is therefore the object of the present invention to provide a transmission of the type referred to above with a reliable arrangement for the interconnection of the trunnions for firm control of their cooperation.